What is the ozone?
Ozone is a gas composed of three oxygen atoms (O3). It is formed naturally in the upper levels of the earth's atmosphere by high-energy ultraviolet radiation from the sun. The radiation breaks down oxygen molecules (O2), releasing free atoms (O), some of which bond with other oxygen molecules to form ozone (O3). »

The initial step in the depletion of stratospheric ozone by human activities is the emission gases contain various combinations of the chemical elements chlorine, fluorine, bromine, carbon, and hydrogen that are often described with the general term ozone depleting substances.»